Navien and cast iron rads?

[Toronto123]

I purchased a house last year that has a Navien CH240 combi boiler feeding the house rads and hot water.
The rads are cast iron and the navien is relatively new (3 years old). I am having never ending issues with this unit. I had to have the main circuit board replaced and as part of a basement renovation, I had my plumber remove the rads. My plan is to move the navien and a company who specializes in tankless units told me the navien is not intended for my house since it wont work properly with cast iron rads and the iron piping i have. He said i really need to replace the unit completely unless we install some sort of additional filtering to clean the water - otherwise he said the unit likely wont last a few years at most.

Since we removed the rads i now have no hot water - we have an E002 error which is low pressure. Im thinking air must have got into the pipes when we removed the rads. However, the heating company is saying they told me the unit wouldnt last and is recommending a full replacement of this relatively new unit.

Question 1: Can anyone confirm that a Navien can or cant work with cast iron rads and iron pipes?
Question 2: Is it possible this E002 is just caused by an air pocket in the pipes.

We know the install of the navien is not correct as it doesnt have a secondary loop, a secondary pump as its supposed to - im hoping a proper reinstall of the existing unit will be sufficient rather than a costly full replacement and im looking for input from anyone who can answer my above 2 questions

Thanks

 

[QueBall]

E002 is low water pressure on the heating loop.
Did you clean your filters and have you done a flush/de-scale maintenance on the tankless unit every 6-12 months? (More often for hard water especially if you do not have a de-scale filter on the input water supply)

Clean out your filters, do a flush on the unit and if still not working you can consider removing the water pressure sensor and checking if it's clogged. Possibly replace that sensor. WPS part number 20007924A. Cost is about $20 or free if still on warranty and you call Navien and they agree part needs replacement. If you find evidence of debris stuck in it you should probably replace as it got past the filter. Should call Navien if there is debris here to see what you should do next as you may need to flush or dismantle more of the heat exchanger to get it all out.

So we are assuming there is no leak in your heating loops at the radiators or anywhere else. Of course if it's leaking somewhere and water is escaping the heating loop, that is the obvious cause of the problem and the boiler is not the issue. You do not have any hot water taps on the radiator line right, because that would be stupid.

The service manual states:
E002 is a self clearing code. It should go away if automatic refilling recovers the pressure. It can lock out if filling does not complete in 3 minutes.
The system refills water if water level of 7.3PSI or lower is detected for over 4 seconds.
The system stops filling water level at 12PSI (depending on setting. What is your domestic water supply pressure, this boiler requires minimum 15PSI to operate)
Filling is stopped forcefully if the water level is 7.4PSI or higher after 3 minutes from starting of water refilling.
If you are not using the Navien auto supplement feature you must have your own water supplement connection from the domestic supply to the heating primary loop to keep it above 7.4PSI.

Steps to troubleshoot:
Check if cold water valve is closed, frozen or stuck.
Check if auto feeder valve filter is clogged with debris. (pipe cuttings left in pipes often get trapped if lines are not flushed after plumbing work is done)
Check if water flows through condensing hose could indicate defective heat exchanger. (Only a trickle should come out while gas is burning)
Check for leak in heating loop. If you presurize and then isolate the heating loop and you loose pressure over time in the expansion tank it likely indicates a leak.

I will let others comment on suitability for use with cast iron. I would think it's no big deal other than draining it and checking filters on a regular basis, but you do that no matter what kind of pipes and radiators you have. They would mention it in the manual if iron were a big problem. That explanation makes no sense to me.

There is also the possibility your plumber doesn't know what they are doing and backflow preventors or thermal expansion are screwed up causing your pressure issue. Sounds like your plumber is looking for excuses. Is the company that you brought in that specializes in tankless do boilers and heating too, do they deal with Navien specifically?


Link to service manual:
http://bostonheatingsupply.com/Navien/CH Service Manual.pdf

 

[Sponsor]

 

[Dana]

There is no inherent problem with using cast iron radiators. If the rads have a lot of old scale and corrosion it's possible to treat the water to inhibit corrosion, and it's worth installing a decent filter, but the high thermal mass of the water volume is GOOD for getting maximum efficiency out of the thing.

A guy posting here under the handle BadgerboilerMN is a pro with real-world experience with Naviens & cast iron, and should be able to fill in the specifics about which water treatments should/should-not be used, and the filter specifics, etc. If he doesn't respond here, open a conversation with him on this site.